1. Field of the Invention
This invention relates to stereoscopic display methodologies and systems. More particularly, this invention relates to page flipping stereoscopic display methodologies and systems as well as apparatus used therein.
2. State of the Art
Stereoscopic display systems display two perspective images in such a way that each eye of the observer sees only one of the two images. There are many systems in existence that provide this capability through various methods. One of these methods in commonly referred to as “page flipping” or frame-sequential stereo video. In such methods, left and right perspective images are time-division multiplexed and thus displayed during different display periods (i.e., left and right perspective image display periods). Stereoscopic glasses (e.g., shutter-type or polarization-type glasses) are used to ensure that the left perspective images are presented to the left eye during the left perspective image display periods and that the right perspective images are presented to the right eye during the right perspective image display periods.
Autostereoscopic systems have been developed that utilize optics (e.g., lenticular systems, parallax barrier, mirror systems, etc.) to present the left perspective images to the left eye and the right perspective images to the right eye without the need for glasses. Such systems are costly and suffer from various technical problems such as limited depth of field, low brightness, and constrained view regions (i.e., the observer(s) are required to be located in limited viewing area(s) relative to the display). Eastman Kodak has developed an autostereoscopic display system that employs two liquid crystal on silicon (LCOS) spatial light modulators. The LCOS spatial light modulator is a micro-display technology which is related to a transmissive liquid crystal display panels but works differently. The liquid crystal material has a twisted nematic structure like a transmissive liquid crystal display, but it is sealed directly to the surface of a silicon chip. The electronic drivers controlling the crystals' alignment are etched into the silicon. Using these, several million pixels can fit in an area as small as one square inch. The chip is coated with a metal reflecting layer, which means that the LCOS display is highly reflective (rather than transmissive). Color is created in a variety of ways. The simplest approach is to include three LCOS panels, one each for red, green and blue light elements. An alternative approach employs field sequential color techniques (which uses a color wheel and fast electronic switching to separate hues), which enables just one LCOS panel to be used, making the product cheaper. LCOS-based displays are advantageous in that they provide very good resolution, high contrast ratio (typically 1,000:1) and large screen/display at reasonable costs.
The Eastman Kodak system employs the simple 3-panel approach for each one of the two LCOS spatial modulators. One LCOS spatial light modulator provides image formation for the left eye, while the other LCOS spatial light modulator provides image formation for the right eye. A curved mirror and curved diffusers project the left and right images to the pupils of the viewer. The user's eye position is tracked by infrared face imaging. Eye position information is fed to an image generator, which adjusts the rendering viewpoints in both the left and right channels simultaneously. This system is costly as it requires two separate LCOS-based spatial light modulators as well as complex optical components, eye-tracking components and rendering components.
Page flipping stereoscopic display systems are typically realized with a cathode ray tube (CRT) display that is adapted to operate in a progressive scan mode that alternately displays a left perspective image and a right perspective image. Such systems provide adequate performance but are limited by their screen size and weight. With this in mind, users have attempted to employ the prior art page flipping stereoscopic display methodologies to active-matrix liquid-crystal display (LCD) panels. Such panels advantageously provide for increased screen size and significant reductions in weight. However, when used for page flipping stereoscopic viewing, the line-based update mechanisms employed by LCD panels cause significant cross-frame image interference where the pixels from a left perspective image are displayed concurrently with pixels from a right perspective image as shown in FIG. 1. Such interference degrades the image quality and limits the commercial acceptability of page-flipping LCD-based stereoscopic display systems. These limitations are also applicable to page-flipping LCOS-based stereoscopic display systems.